Glass chopped strand mat, method for producing same, automotive molded ceiling material, and method for producing same

ABSTRACT

Provided is a high-quality and high-functionality glass chopped strand mat which is applicable to recent automotive molded ceiling materials which have excellent design and reduced weights. The glass chopped strand mat is a glass chopped strand mat (M) produced by forming glass chopped strands (S) into a sheet, in which the ratio of a tensile strength in a width direction to a tensile strength in a longitudinal direction (the width direction/the longitudinal direction) of the glass chopped strand mat (M) is at least 0.73 and less than 1.00, and the tensile strength in the width direction is not less than 80 N as measured in a tensile rupture test conducted according to the Japanese Industrial Standards (Section 7.25 of JIS R3420 (2006)), where the width of a test specimen is 150 mm.

The present application is a U.S. National Stage Application based onand claiming benefit of and priority under 35 U.S.C. §371 toInternational Application No. PCT/JP2012/081475, filed 5 Dec. 2012,which in turn claims benefit of and priority to Japanese Application No.2011-278988, filed 20 Dec. 2011, the entirety of each of which is herebyincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to glass chopped strand mats produced byforming glass chopped strands into a sheet, and methods for producingthe glass chopped strand mats. The present invention also relates toautomotive molded ceiling materials including the glass chopped strandmats, and methods for producing the automotive molded ceiling materials.

BACKGROUND ART

A glass chopped strand mat is conventionally used as a reinforcementmember of a glass fiber reinforced plastic (GFRP) molded product, suchas a bathtub or a septic tank. The glass chopped strand mat has inrecent years been employed as a reinforcement base of an automotivemolded ceiling material. The automotive molded ceiling material in whichthe glass chopped strand mat is attached to both sides of a foamedpolyurethane sheet has been developed.

The glass chopped strand mat is produced as follows. Initially, a glassfiber is cut into pieces having a predetermined length to obtain glasschopped strands. Next, the glass chopped strands are distributed anddeposited on a conveying means such as a conveyor to be formed into theshape of a sheet. The glass chopped strands are subjected to a pluralityof steps while being conveyed by the conveyor. For example, the stepsinclude spraying a binder to the glass chopped strands, heating theglass chopped strands with the adhering binder, and cooling and pressingthe glass chopped strands after the heating, and the like. The glasschopped strand mat produced by these steps is wound around a core into aroll by a winding machine or the like before shipment.

The glass chopped strand mat which has been wound into a roll isprocessed into an automotive molded ceiling material as follows. Theglass chopped strand mat is temporarily unwound. An adhesive is appliedto the glass chopped strand mat. The glass chopped strand mat is woundagain. Thereafter, the glass chopped strand mat with the adhesive, afoamed urethane sheet as a base member, and the like are attachedtogether and molded into an automotive molded ceiling material having adesired shape.

In recent years, as the diversity of automotive design has increased,there has been a demand for a ceiling surface having a more complicatedshape in order to further improve the design. To meet such a demand, theglass chopped strand mat used for a ceiling surface is required to havea high level of flexibility. The flexibility of the glass chopped strandmat is preferably increased by distributing glass chopped strands in theglass chopped strand mat as uniformly in all directions as possible. Theflexibility may also be increased by reducing the amount of the binderadded to the grass chopped strands. In these techniques, however, asufficient tensile strength may not be imparted to the glass choppedstrand mat, and in particular, when the glass chopped strand mat withthe applied adhesive is temporarily unwound in the above-describedprocess of producing the automotive molded ceiling material, the glasschopped strand mat may not withstand the tensile force and may be brokenalong the width direction.

Advances in automotive weight reduction have led to a demand for areduction in the weight of the automotive molded ceiling material. Thisdemand may be satisfied by reducing the weight of the glass choppedstrand mat itself by reducing the amount of glass chopped strands whichare used as a material for the glass chopped strand mat. However, whenthe weight of the glass chopped strand mat is reduced by reducing theamount of glass chopped strands, the tensile strength of the glasschopped strand mat obtained decreases, and therefore, the glass choppedstrand mat is more likely to be broken in any process. The break of theglass chopped strand mat directly leads to a molding defect, aninterruption of the producing process, or the like.

On the other hand, when the tensile strength of the glass chopped strandmat becomes excessive, the flexibility decreases, and therefore, whenthe automotive molded ceiling material is molded, a molding defect, suchas a depression or a dimple, which is called a “sink mark,” is likely tooccur in the surface of the automotive molded ceiling material. As aresult, the yield of the automotive molded ceiling materialdeteriorates, leading to a decrease in production efficiency.

Therefore, it is necessary for the glass chopped strand mat used in theautomotive molded ceiling material to have both a good flexibility and agood tensile strength.

Heretofore, a known glass chopped strand mat has a difference in tensilestrength between the mat width direction and the mat longitudinaldirection (see Patent Document 1). Patent Document 1 describes a methodfor producing a glass chopped strand mat which is formed of glasschopped strands having an average strand mass density of 10 to 20 tex,has a weight of 50 to 150 g/m², an average tensile strength in the matwidth direction of not more than 150 N which is measured in a tensilerupture test conducted according to Annex 13 of JIS R3420 (1999), thestandard deviation of the tensile strength being not more than 50 N, andan average tensile strength in the mat longitudinal direction of notless than 100 N. It is considered that this glass chopped strand mat hassuch good quality that it has a sufficient strength, and there is only asmall risk of a problem with appearance, such as a pattern which standsout from the surface of a molded product in the shape of the glasschopped strand after the glass chopped strand mat is molded into anautomotive molded ceiling material.

Note that Annex 13 of JIS R3420 (1999), which describes a “method fordetermining the tensile breaking force for textile glass mats,” is atranslation of ISO 3342, “Textile glass—Mats—Determination of tensilebreaking force,” Third Edition, 1995, where no subject matter ischanged.

CITATION LIST Patent Literature

-   Patent Document 1: Japanese Unexamined Patent Application    Publication No. 2005-350815

SUMMARY OF INVENTION Technical Problem

The glass chopped strand mat of Patent Document 1 has an improvedtensile strength, but does not necessarily have a sufficient flexibilitywhich allows itself to be processed into a desired shape. Theflexibility and tensile strength of a glass chopped strand matsignificantly depends on the balance between the tensile strength in thewidth direction and the tensile strength in the longitudinal directionof the glass chopped strand mat. In the glass chopped strand mat ofPatent Document 1, although the tensile strength in the width directionand the tensile strength in the longitudinal direction are separatelyspecified, a relationship therebetween is not taken into consideration.Therefore, in the glass chopped strand mat of Patent Document 1,although a significant problem does not arise with the tensile strengthsin both of the directions, the flexibility of the whole mat is notsufficient, and therefore, it may be difficult to mold the glass choppedstrand mat into a desired shape of an automotive molded ceilingmaterial.

As described above, at present, a glass chopped strand mat having a goodbalance between flexibility and tensile strength, i.e., having both agood flexibility and a good tensile strength, has not yet beendeveloped. With these circumstances in mind, the present invention hasbeen made. It is an object of the present invention to provide ahigh-quality and high-functionality glass chopped strand mat which isapplicable to, for example, recent automotive molded ceiling materialswhich have excellent design and reduced weights, with attention given toa relationship between the tensile strength in the width direction andthe tensile strength in the longitudinal direction of the glass choppedstrand mat.

Solution to Problem

To achieve the above object, a glass chopped strand mat according to thepresent invention has the following characteristic features.

The glass chopped strand mat is a glass chopped strand mat produced byforming glass chopped strands into a sheet, in which

the ratio of a tensile strength in a width direction to a tensilestrength in a longitudinal direction (the width direction/thelongitudinal direction) of the glass chopped strand mat is at least 0.73and less than 1.00.

As described in the TECHNICAL PROBLEM section, in the conventional art,it is difficult to provide a glass chopped strand mat which has aflexibility sufficient to allow itself to be easily molded into adesired shape and is also not easily broken. This is mainly because thetensile strength in the width direction and the tensile strength in thelongitudinal direction are separately determined without taking intoconsideration the flexibility of the glass chopped strand mat.

In this regard, in the glass chopped strand mat of this configuration,the ratio of the tensile strength in the width direction to the tensilestrength in the longitudinal direction (the width direction/thelongitudinal direction) of the glass chopped strand mat is set to atleast 0.73 and less than 1.00, and therefore, a sufficient flexibilitycan be ensured in both the width direction and the longitudinaldirection of the glass chopped strand mat. If the tensile strength inthe width direction is set so that an abnormality such as rupture doesnot occur, a sufficient tensile strength is also necessarily obtained inthe longitudinal direction. As a result, the glass chopped strand matcan have a good balance between flexibility and tensile strength, i.e.,have both a good flexibility and a good tensile strength.

In the glass chopped strand mat of the present invention, the tensilestrength in the width direction is preferably not less than 80 N asmeasured in a tensile rupture test conducted according to the JapaneseIndustrial Standards (Section 7.25 of JIS R3420 (2006)), where the widthof a test specimen is 150 mm.

In the glass chopped strand mat of this configuration, the tensilestrength in the width direction is not less than 80 N as measured in atensile rupture test conducted according to the Japanese IndustrialStandards (Section 7.25 of JIS R3420 (2006)), where the width of a testspecimen is 150 mm. Therefore, the glass chopped strand mat has asufficient tensile strength in the width direction for a moldingprocess. In this case, the glass chopped strand mat also necessarily hasa tensile strength of not less than 80 N in the longitudinal direction.Therefore, the glass chopped strand mat is not likely to be broken inany of various steps while a sufficient flexibility is maintained whichallows the glass chopped strand mat to be easily molded into a desiredshape. Therefore, the glass chopped strand mat can have a good balancebetween flexibility and tensile strength, i.e., have both a goodflexibility and a good tensile strength.

In the glass chopped strand mat of the present invention, the glasschopped strands preferably have a weight of 50 to 150 g/m², where theweight is the mass per unit area.

In the glass chopped strand mat of this configuration, the glass choppedstrands have a weight of as low as 50 to 150 g/m², where the weight isthe mass per unit area. Therefore, the glass chopped strand mat can havea good balance between flexibility and tensile strength, i.e., has botha good flexibility and a good tensile strength, and a thinner thicknessand a lighter weight.

To achieve the above object, a glass chopped strand mat productionmethod according to the present invention has the followingcharacteristic features.

The glass chopped strand mat production method is a method for producinga glass chopped strand mat by forming glass chopped strands into asheet, including:

a first conveying step of continuously conveying the glass choppedstrands in a distributed form while spraying resin powder serving as abinder onto the glass chopped strands; and

a second conveying step of continuously conveying the glass choppedstrands with the adhering resin powder while performing a heatingtreatment on the glass chopped strands at a temperature higher than themelting point of the resin powder,

in which

a conveying speed in the second conveying step is higher than aconveying speed in the first conveying step, and the differencetherebetween is 3 to 8 m/min, and the ratio of a tensile strength in awidth direction to a tensile strength in a longitudinal direction (thewidth direction/the longitudinal direction) of the glass chopped strandmat is at least 0.73 and less than 1.00.

The method for producing a glass chopped strand mat by forming glasschopped strands into a sheet includes the first conveying step ofcontinuously conveying the glass chopped strands in a distributed formwhile spraying resin powder serving as a binder onto the glass choppedstrands, and the second conveying step of continuously conveying theglass chopped strands with the adhering resin powder while performing aheating treatment on the glass chopped strands at a temperature higherthan the melting point of the resin powder. The conveying speed in thesecond conveying step is set to be higher than the conveying speed inthe first conveying step, and the difference therebetween is set to 3 tom/min. As a result, when the glass chopped strands are transferred fromthe first conveying step to the second conveying step, the glass choppedstrands are pulled in the conveying direction to be aligned to anappropriate extent. Therefore, the tensile strength in the conveyingdirection increases, and the thickness of the glass chopped strand matthus obtained decreases, resulting in a reduction in weight. Inaddition, according to the results of the extensive study by the presentinventors, it has been found that if the difference between theconveying speed in the second conveying step and the conveying speed inthe first conveying step is set to 3 to 8 m/min, the glass choppedstrand mat is not likely to be broken in any of various steps while asufficient flexibility is maintained which allows the glass choppedstrand mat to be easily molded into a desired shape. It has also beenfound that if the ratio of the tensile strength in the width directionto the tensile strength in the longitudinal direction (the widthdirection/the longitudinal direction) of the glass chopped strand mat isset to at least 0.73 and less than 1.00, a sufficient flexibility can beensured in both the width direction and the longitudinal direction ofthe glass chopped strand mat. Here, if the tensile strength in the widthdirection is set so that an abnormality such as rupture does not occur,a sufficient tensile strength is also necessarily obtained in thelongitudinal direction. Therefore, the glass chopped strand matproduction method of this configuration can be used to produce a glasschopped strand mat having a good balance between flexibility and tensilestrength, i.e., having both a good flexibility and a good tensilestrength, and a lighter weight.

To achieve the above object, an automotive molded ceiling materialaccording to the present invention has the following characteristicfeatures.

The automotive molded ceiling material is an automotive molded ceilingmaterial including a glass chopped strand mat produced by forming glasschopped strands into a sheet, and a flexible base sheet on one or bothsides of which the glass chopped strand mat is provided, in which

the ratio of a tensile strength in a width direction to a tensilestrength in a longitudinal direction (the width direction/thelongitudinal direction) of the glass chopped strand mat is at least 0.73and less than 1.00.

The automotive molded ceiling material of this configuration includes aglass chopped strand mat produced by forming glass chopped strands intoa sheet, and a flexible base sheet on one or both sides of which theglass chopped strand mat is provided, and the ratio of the tensilestrength in the width direction to the tensile strength in thelongitudinal direction (the width direction/the longitudinal direction)of the glass chopped strand mat is set to at least 0.73 and less than1.00. Therefore, a sufficient flexibility can be ensured in both thewidth direction and the longitudinal direction of the glass choppedstrand mat, and therefore, the glass chopped strand mat can be used tosatisfactorily perform a molding process to provide an automotive moldedceiling material even having a complicated shape, for example. Here, ifthe tensile strength in the width direction is set so that anabnormality such as rupture does not occur, a sufficient tensilestrength is also necessarily obtained in the longitudinal direction. Ifthe glass chopped strand mat which has a good balance betweenflexibility and tensile strength (i.e., has both a good flexibility anda good tensile strength) is provided on one or both sides of a flexiblebase sheet, an automotive molded ceiling material which is reinforcedand has a good design flexibility can be provided.

To achieve the above object, an automotive molded ceiling materialproduction method according to the present invention has the followingcharacteristic features.

The method includes

a layering step of putting the glass chopped strand mat of the presentinvention on one or both sides of a flexible base sheet.

The automotive molded ceiling material production method of thisconfiguration includes a layering step of putting the glass choppedstrand mat of the present invention on one or both sides of a flexiblebase sheet. Therefore, for example, a molding process can besatisfactorily performed to impart a complicated shape to the automotivemolded ceiling material. In other words, if the glass chopped strand matwhich has a good balance between flexibility and tensile strength (i.e.,has both a good flexibility and a good tensile strength) is provided onone or both sides of a flexible base sheet, an automotive molded ceilingmaterial which is reinforced and has a good design flexibility can beprovided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing an overall configuration of aglass chopped strand mat production apparatus for producing a glasschopped strand mat according to the present invention.

FIG. 2 is a cross-sectional view of a portion of an automotive moldedceiling material according to the present invention.

DESCRIPTION OF EMBODIMENTS

A glass chopped strand mat according to the present invention and amethod for producing the glass chopped strand mat, and an automotivemolded ceiling material according to the present invention and a methodfor producing the automotive molded ceiling material, will be describedhereinafter with reference to FIGS. 1 and 2. Note that, in the presentspecification, an apparatus for producing the glass chopped strand matis also described for the sake of convenience. Note that the presentinvention is not intended to be limited to embodiments described belowor configurations shown in the drawings.

<Apparatus for Producing Glass Chopped Strand Mat>

FIG. 1 is a schematic diagram showing an overall configuration of aglass chopped strand mat production apparatus 100 for producing a glasschopped strand mat according to the present invention (hereinaftersimply referred to as a “production apparatus”).

The production apparatus 100 produces a glass chopped strand mat fromglass chopped strands. The production apparatus 100 mainly includes achamber 10, a cutting device 20, a distribution conveyor 30, a bindersprayer 40, a first conveyor 50, a second conveyor 60, a heating furnace70, a cold press roller 80, a winding machine 90, etc.

The distribution conveyor 30, the first conveyer 50, and the secondconveyor 60 are successively positioned in this stated order fromupstream to downstream. These conveyors are driven by respective motorsD. The conveying speeds (the movement speeds of the belts) of theconveyors are controlled by a computer (control means) 11. Note that aworker may manually adjust the conveying speed of each conveyor asappropriate.

The distribution conveyor 30 includes a belt on which glass choppedstrands are distributed and put. The distribution conveyor 30 isprovided below the chamber 10 which accommodates glass chopped strands.The cutting device 20 which cuts a glass fiber F described below isattached to a glass fiber inlet 10 a provided in a top portion of thechamber 10. The cutting device 20 includes a cutter roller 21 and arubber roller 22. The glass fiber F is fed between the rotating cutterroller 21 and rubber roller 22 to be continually cut, whereby glasschopped strands S are produced. The glass chopped strands S fall bytheir own weight in the chamber 10 and are substantially uniformlydistributed and put on the belt of the distribution conveyor 30.

The binder sprayer 40 is provided above the first conveyor 50. Thebinder sprayer 40 sprays a binder A described below toward the glasschopped strands S on the belt of the first conveyor 50. Note that awater sprayer (not shown) may be effectively provided above or below thefirst conveyor 50, upstream of the binder sprayer 40, in order to allowthe binder A to more easily adhere to the glass chopped strands S.

The heating furnace 70 is provided halfway through the second conveyor60, surrounding the belt. The heating furnace performs a heatingtreatment on an object on the second conveyor 60 which is being movedthrough the heating furnace 70. Therefore, the belt of the secondconveyor 60 is formed of a heat resistant material, such as a metal. Thecold press roller 80 is provided downstream of the second conveyor 60.The cold press roller 80 presses the heated object while cooling theobject.

(Method for Producing Glass Chopped Strand Mat)

The glass chopped strand mat of this embodiment is produced by a step ofpreparing the glass chopped strands S, a distribution and putting step,a first conveying step, a second conveying step, a cold press step, anda winding step. Of these steps, the first and second conveying stepshave a characteristic feature of the present invention and are essentialto the present invention. The above steps will now be described.

<Glass Chopped Strand Preparation Step>

As a preliminary step of the production of a glass chopped strand mat,the glass chopped strands S are prepared. A glass material is heated toobtain hot melted glass in a glass melting furnace (not shown) providedon the production line. The glass material contains components fromwhich a glass fiber of E-glass can be produced. The melted glass isclarified and homogenized, and thereafter, is caused to flow via afeeder (not shown) into a bushing (not shown). The base plate of thebushing has a plurality of bushing nozzles. The melted glass isdischarged from the bushing nozzles and spun into a fibrous glassmonofilament. After the glass monofilament is cooled, a bundling agentis applied thereto. A plurality of the glass monofilaments are bundledtogether into a glass fiber F, which is then wound into a glass cake 1.The glass fiber F extracted from the glass cake 1 is fed into thecutting device 20 provided in the top portion of the chamber 10 and isthen cut into pieces having a length of about 50 mm. Thus, in thisembodiment, the preparation step of cutting the glass fiber F into theglass chopped strands S is performed. Note that the glass choppedstrands S do not necessarily need to be prepared immediately before theproduction of the glass chopped strand mat, and alternatively, may bepreviously prepared. In this case, for example, the glass choppedstrands S which are accommodated in a container (e.g., a flexiblecontainer) are fed directly into the chamber 10.

<Distribution and Putting Step>

The glass chopped strands S obtained by the glass chopped strandpreparation step fall onto the belt of the distribution conveyor 30 inthe chamber 10. A suction device 33 including a suction duct 31 and ablower 32 is provided below the belt on which the glass chopped strandsS are deposited, and a negative pressure is applied to the belt. As aresult, the glass chopped strands S are attracted to a surface of thebelt while being substantially uniformly distributed and put on the beltof the distribution conveyor 30, and therefore, are settled withoutbeing scattered around. The conveying speed in the distribution andputting step is preferably 69 m/min to 74 m/min. If the conveying speedis within this range, the glass chopped strands S can be deposited intoan appropriate thickness, and the production time of the glass choppedstrand mat can be significantly reduced. The glass chopped strands Swhich have been deposited on the belt of the distribution conveyor 30 tobe formed into the shape of a sheet are conveyed to a downstream pointfor the next step.

<First Conveying Step>

The glass chopped strands S which have been deposited to be formed intothe shape of a sheet are moved to the first conveyor 50. The bindersprayer 40 is provided above the first conveyor 50. The binder sprayer40 sprays the binder (resin powder) A to the surfaces of the glasschopped strands S. The addition of the binder A to the glass choppedstrands S allows the glass chopped strands S to stick together by aheating treatment described below, so that the mat shape can bemaintained. The binder A is preferably a powder of thermoplastic resin(e.g., powdered polyester resin (e.g., NEW TRACK 514 produced by KaoCorporation)). Other examples of the available thermoplastic resinpowder include resin powders of nylon, polyethylene, polystyrene,polypropylene, polyvinyl chloride, etc.

A water sprayer (not shown) may be effectively provided upstream of thebinder sprayer 40. The water sprayer sprays water toward the glasschopped strands S on the belt of the first conveyor 50. If the glasschopped strands S are previously wetted with water, the binder A moreeasily adheres to the surfaces of the glass chopped strands S due to theaction of the surface tension of the water, and therefore, the glasschopped strands S stick together more effectively. Therefore, even ifthe weight (mass per unit area of glass chopped strands S) is set to therange of 50 to 150 g/m², which is lower than a typical weight, the glasschopped strand mat, which is the final product, can have a good balancebetween flexibility and tensile strength, i.e., have both a goodflexibility and a good tensile strength. The glass chopped strand matcan also have a thinner thickness and a lighter weight. Note that theweight of the glass chopped strand mat is preferably 70 to 140 g/m²,more preferably 80 to 120 g/m².

A vibrator 51 is provided below the belt of the first conveyor 50 onwhich the glass chopped strands S are deposited, to vibrate the belt ofthe first conveyor 50. This causes the binder A scattered to thesurfaces of the glass chopped strands S to enter gaps between the glasschopped strands S which have been deposited to be formed into the shapeof a sheet. As a result, the binder A adheres uniformly to all the glasschopped strands S.

The glass chopped strands S on the first conveyor 50 are conveyed to thedownstream second conveyor 60 with the binder A uniformly adhering tothe glass chopped strands S.

<Second Conveying Step>

The heating furnace 70 surrounds the belt of the second conveyor 60. Thetemperature of atmosphere in the heating furnace 70 is controlled by acomputer 11 to be appropriately adjusted to a temperature higher than orequal to the melting point of the synthetic resin included in thesprayed binder A, depending on the type of the binder A. Note that thetemperature of the heating furnace 70 may be manually adjusted by aworker. The glass chopped strands S with the adhering binder A on thebelt of the second conveyor 60 are subjected to the heating treatmentwhile passing through the heating furnace 70, whereby the binder A issoftened and melted. As a result, the glass chopped strands S sticktogether (the glass chopped strands S after being heated are referred toas “glass chopped strands S′” to discriminate from those before beingheated). Because the belt of the second conveyor 60 is thus exposed tohigh temperature, the belt is formed of a heat resistant material, suchas a metal.

In this embodiment, the conveying speed in the second conveying step isset to be higher than the conveying speed in the first conveying step.As a result, when the glass chopped strands S are transferred from thefirst conveying step (the first conveyor 50) to the second conveyingstep (the second conveyor 60), the glass chopped strands S are pulled inthe conveying direction to be aligned to an appropriate extent.Specifically, the glass chopped strands S are generally uniformlydistributed and put on the distribution conveyor 30, and are thenconveyed to the first conveyor 50 while being kept in such a state, andtherefore, are generally oriented in random directions in the firstconveying step. Next, immediately after the glass chopped strands S aretransferred to the second conveying step, the conveying speed of theglass chopped strands S increases. At this time, a tension occurs in theglass chopped strands S due to the difference in conveying speed. As aresult, each glass chopped strand S is stretched in the conveyingdirection, and therefore, the glass chopped strands S have equal fiberlengths in the conveying direction. As a result, the tensile strength inthe conveying direction increases, and therefore, the thickness of thedeposition of the glass chopped strands S decreases, resulting in adecrease in weight per unit area. This leads to a reduction in weight ofthe glass chopped strand mat, which is the subsequent final product.

According to the result of the extensive study conducted by the presentinventors, it has been found that if the difference in conveying speedbetween the second conveying step and the first conveying step is set to3 to 8 m/min, the glass chopped strand mat is not likely to be broken inany of various steps while a sufficient flexibility is maintained whichallows the glass chopped strand mat to be easily molded into a desiredshape. If the conveying speed difference is less than 3 m/min, the glasschopped strands S are less aligned, and therefore, the tensile strengthin the longitudinal direction is not sufficient and wrinkles are likelyto occur in the surface of the glass chopped strand mat, which is thefinal product. On the other hand, if the conveying speed difference ismore than 8 m/min, the weight of the glass chopped strand mat, which isthe final product, decreases, and therefore, the thickness decreases, sothat a very thin portion or a void is likely to occur in the matsurface, resulting in a significant decrease in tensile strength.

In this embodiment, the second conveying speed is preferably set to 75to 78 m/min. This conveying speed is considerably high compared toconventional production conditions. In general, when the glass choppedstrands S are conveyed at such a high speed, an excessive tension occursin the conveying direction, and therefore, the glass chopped strands Sare easily separated from each other. However, in this embodiment, asdescribed above, the difference in conveying speed between the secondconveying step and the first conveying step is set to 3 to 8 m/min, andtherefore, the glass chopped strands S are not separated from each otherwhile being conveyed, and therefore, the glass chopped strand mat is notbroken. Therefore, the time it takes to produce the glass chopped strandmat, which is the final product, can be significantly reduced.

<Cold Press Step>

The cold press step of processing the glass chopped strands S′ whichhave been heated, into a mat, is performed by the cold press roller 80which is provided downstream of the second conveyor 60. The cold pressroller 80 includes a pair of rollers. The glass chopped strands S′ withthe melted binder A is conveyed to the cold press roller 80 and passedthrough the nip. The glass chopped strands S′ are cooled and pressed bybeing passed through the cold press roller 80, whereby the glass choppedstrands S′ are bound together. As a result, the glass chopped strand matM is produced. The cold press roller 80 air-cools the glass choppedstrands S′. Alternatively, the glass chopped strands S′ may be activelycooled with cooling water flowing inside the cold press roller 80.

<Winding Step>

The winding step is performed by the winding machine 90 which isprovided downstream of the cold press roller 80. The glass choppedstrand mat M which has been pressed is wound around the core of thewinding machine 90 to form a roll product.

(Glass Chopped Strand Mat)

The glass chopped strand mat M of this embodiment is formed by the firstand second conveying steps of the above production method, andtherefore, has a good balance between flexibility and tensile strength(i.e., has both a good flexibility and a good tensile strength) and alighter weight. Specifically, the ratio of the tensile strength in thewidth direction to the tensile strength in the longitudinal direction(the width direction/the longitudinal direction) of the glass choppedstrand mat M is set to at least 0.73 and less than 1.00. The tensilestrength ratio is calculated based on the tensile strengths in the widthand longitudinal directions of the glass chopped strand mat M which aremeasured by a tensile rupture test conducted according to the JapaneseIndustrial Standards (Section 7.25 of JIS R3420 (2006)), where the widthof a test specimen is 150 mm. Section 7.25 of JIS R3420 (2006) specifiesas follows.

<7.25 of JIS R3420 (2006)>

7.25 Tensile strength of mats. A method for testing the tensile strengthof mats is specified. The method is intended for chopped strand mats butis equally applicable to continuous filament mats.

7.25.1 Principle. A pre-conditioned test specimen of standard dimensionsis subjected to tension by a suitable device which indicates the tensilebreaking force on a recorder or the like. The maximum force required tobreak the test specimen in a tensile test carried to rupture isgenerally expressed in newtons (N).

7.25.2 Testing apparatus. The following testing machines shall be used.

a) Tensile-testing machine. All testing machines shall include thefollowing elements.

-   -   1) A pair of suitable clamps to grip the specimen. They shall        have a width of 160 mm and a minimum depth of 25 mm. The faces        of the clamps shall be plane and parallel, shall ensure uniform        pressure over the whole width of the test specimen, and shall        prevent it from slipping. The clamps shall also ensure, at all        times, alignment with the direction of the force applied to the        test specimen. The initial distance between the clamps shall be        200 mm.    -   2) A means for applying tension to the test specimen.    -   3) A mechanism that will continuously indicate or record the        force sustained by the test specimen. The mechanism shall be        practically free from inertia at the specified speed of testing        and shall indicate the force with an accuracy within 1% of the        true value. There are two types of testing machines recommended,        i.e., one having a constant rate of extension and one having a        constant rate of loading. If only such testing machines are        available, they may be used by agreement between interested        parties, but the results from different types of testing        machines cannot necessarily be compared.    -   4) The maximum error in the indicated force, at any point in the        range in which the testing machine is used, shall not exceed 1%        of the true force. The acceptable error in the clamp separation        indication value shall not exceed 2 mm. The accuracy of the        tensile-testing machine shall be verified, for example, by means        of calibrated springs with appropriate characteristics.

b) Equipment for producing a suitable preconditioning atmosphere.

c) Equipment for producing and maintaining the standard laboratory testatmosphere.

d) Hard Template.

-   -   1) For chopped strand mat: 150 mm (width)×316 mm (length) or 300        mm (width)×300 mm (length)    -   2) For continuous strand mat: 75 mm (width)×316 mm (length)

e) Specimen trimming tool. An appropriate tool, such as a knife,scissors, or a disc cutter.

f) Stopwatch.

7.25.3 Conditioning and test atmosphere.

a) Conditioning. Carry out in the standard atmosphere specified inSection 4 (Section 4 specifies air temperature t: 23° C., relativehumidity U: 50%).

-   -   1) Condition rolls for 16 h as a standard. Note that the time        may be determined by agreement between interested parties.    -   2) Condition test specimens for 1 h.

b) Test atmosphere. Carry out in the standard atmosphere specified inSection 4.

7.25.4 Test specimen. Before preparing any test specimens, remove anddiscard defects from both sides of a mat to obtain an area free from anydamage. From this area, cut a strip at least 400 mm wide. Handle thisstrip with great care in order to avoid creasing it. Take the sameprecautions with strips cut out as described below. Using the template,cut from this strip the required number of test specimens of 150 mm (or75 mm) (width)×316 mm (length), with the major axis of the specimensparallel to the longitudinal direction of the mat. Cut out thesespecimens (one specimen per 316 mm wide of the mat) ensuring that theyare evenly distributed and equidistant from each other and are not lessthan 10 mm from the edges in the case of trimmed mats.

-   -   At least five specimens are used.    -   If the required number of test specimens cannot be taken from        one strip, test specimens are taken from a plurality of strips,        ensuring that the test specimens are evenly distributed over the        whole mat.    -   It is convenient to cut the specimens from a mat having a        definite mass per unit area.

Note that when there is a request that test specimens are taken usingother methods in production specifications or an individual order, thisshall be recorded in the test report.

7.25.5 Procedure

a) Adjust the distance between the clamps so that the free length of atest specimen is 200 mm.

b) Adjust the speed of the testing machine so that the clamp separationspeed is 200±10 mm/min or 100±10 mm/min.

c) Verify that the clamps are correctly aligned on a straight line andare parallel to each other. Mount the test specimen to the clamps sothat the longitudinal axis of the test specimen coincides with thetensile axis of the tensile tester. Firmly close the clamps evenly, andapply a small tension to the test specimen so that the test specimenextends sufficiently straight. Actuate the tensile tester to elongatethe test specimen to the point of rupture. Record the force required tobreak the test specimen in newtons (N). Test the required number of testspecimens. If the test specimen breaks within 10 mm from the edge of theclamp or slips in the clamp, the result of it is excluded (see 7.25.4).A crack in the test specimen is not a clear break (or rupture), and thisshall be recorded in the test report.

7.25.6 Expression of results. Express the value obtained from each testspecimen in newtons (N). Round the value to 1 N as the tensile breakingforce of the mat. Indicate the confidence levels of the standarddeviation and the average.

The tensile strength ratio of the glass chopped strand mat M of thisembodiment is within a suitable range (at least 0.73 and less than1.00), thereby ensuring a flexibility which is sufficient to allow theglass chopped strand mat M to be molded into a desired shape. If theratio of the tensile strength in the width direction to the tensilestrength in the longitudinal direction (the width direction/thelongitudinal direction) is less than 0.73, the tensile strength in thelongitudinal direction is excessively large, and therefore, theflexibility in the longitudinal direction is significantly lower thanthat in the width direction. As a result, a molding defect is highlylikely to occur when the glass chopped strand mat M is molded into anautomotive molded ceiling material described below. On the other hand,in order to continuously produce the glass chopped strand mat M usingthe production apparatus 100, it is necessary to set the conveying speedin the second conveying step to be invariably higher than the conveyingspeed in the first conveying step. Therefore, as long as the productionapparatus 100 is used, the tensile strength in the longitudinaldirection is not smaller than the tensile strength in the widthdirection, and therefore, the ratio of the tensile strength in the widthdirection to the tensile strength in the longitudinal direction (thewidth direction/the longitudinal direction) does not exceed 1.00.

The tensile strength in the width direction of the glass chopped strandmat M of this embodiment is set to not less than 80 N in a tensilerupture test conducted according to the Japanese Industrial Standards(Section 7.25 of JIS R3420 (2006)), where the width of a test specimenis 150 mm. Therefore, an abnormality such as rupture does not occur inthe width direction of the glass chopped strand mat M during productionor molding. Because the tensile strength ratio is set within a suitablerange (at least 0.73 and less than 1.00), a sufficient tensile strengthis also necessarily obtained in the longitudinal direction. As a result,a good balance between flexibility and tensile strength (i.e., both agood flexibility and a good tensile strength) can be achieved, and alighter weight can be achieved by the weight reduction. Note that if thetensile strength in the width direction is less than 80 N, the tensilestrength is not sufficient during production or molding, and the glasschopped strand mat M is highly likely to break.

(Method for Producing Automotive Molded Ceiling Material)

FIG. 2 is a cross-sectional view of a portion of an automotive moldedceiling material 200 including the glass chopped strand mat M of thepresent invention.

The automotive molded ceiling material 200 is produced as follows. Theabove-described glass chopped strand mat M which has been wound into aroll is temporarily unwound. An adhesive is applied to the surfacethereof. The adhesive may be, for example, an isocyanate adhesive. Theglass chopped strand mat M with the applied adhesive is wound again. Theautomotive molded ceiling material 200 typically includes a front skin91, the glass chopped strand mat M, a foamed urethane sheet 92 which isa base member, and a back skin 93. Each of these members is previouslywound into a roll, and is unwound before the molding process. In themolding process, the front skin 91 (closer to the passenger compartmentof an automobile), a first glass chopped strand mat M, the foamedurethane sheet 92, a second glass chopped strand mat M, and the backskin 93 (closer to the body of an automobile) are stacked on top of eachother successively in this stated order from bottom. Note that the glasschopped strand mat M may be put on only one side of the foamed urethanesheet 92. Thereafter, the multilayer sheet is put into a compressionmold which has a carbide blade at open edges thereof. The compressionmold has the desired shape of the automotive molded ceiling material200. After compression molding, end portions are trimmed to complete theproduction of the automotive molded ceiling material 200.

As described above, the method for producing the automotive moldedceiling material 200 of this embodiment includes the layering step ofputting the glass chopped strand mat M on a foamed urethane sheet 92which is a base sheet. Therefore, the glass chopped strand mat M can beused to satisfactorily perform a molding process to provide anautomotive molded ceiling material even having a complicated shape, forexample. Also, when the glass chopped strand mat M is temporarilyunwound in the producing process of the automotive molded ceilingmaterial 200, the glass chopped strand mat M is not broken in the widthdirection due to tension. Thus, if the glass chopped strand mat M whichhas a good balance between flexibility and tensile strength (i.e., hasboth a good flexibility and a good tensile strength) and a lighterweight is provided on both sides of the flexible foamed urethane sheet92, the automotive molded ceiling material 200 can be reinforced andhave a good design flexibility.

(Automotive Molded Ceiling Material)

As shown in FIG. 2, the automotive molded ceiling material 200 of thisembodiment includes the front skin 91 (closer to the passengercompartment of an automobile), the first glass chopped strand mat M, thefoamed urethane sheet 92, the second glass chopped strand mat M, and theback skin 93 (closer to the body of an automobile). The ratio of thetensile strength in the width direction to the tensile strength in thelongitudinal direction (the width direction/the longitudinal direction)of the glass chopped strand mat M included in the automotive moldedceiling material 200 is set to at least 0.73 and less than 1.00, andtherefore, the glass chopped strand mat M has a good balance betweenflexibility and tensile strength (i.e., has both a good flexibility anda good tensile strength) and a lighter weight. If the glass choppedstrand mat M is provided on both sides of the flexible foamed urethanesheet 92, a molding defect such as a sink mark does not occur whencompression molding is performed on the multilayer sheet to form theautomotive molded ceiling material 200. Therefore, the use of the glasschopped strand mat M allows the automotive molded ceiling material 200of this embodiment to have a high strength and a lighter weight. Also,for example, even an automotive molded ceiling material having acomplicated shape can be satisfactorily provided by a molding process,resulting in a good design flexibility.

EXAMPLES

Examples relating to the glass chopped strand mat of the presentinvention will be described.

In the examples, glass chopped strand mats were produced and testedunder four sets of test conditions that the first conveyor in the firstconveying step had different conveying speeds and the second conveyor inthe second conveying step had the same conveying speed (Examples 1 to4). The tensile strength of the glass chopped strand mat obtained ineach example was measured. Note that the weight (mass per unit area) ofglass chopped strands was 107 g/m² in Examples 1, 2, and 4, and 90 g/m²in Example 3.

The glass chopped strand mats of Examples 1 to 4 were produced by thesame process as that described in the above embodiment using aproduction apparatus of the same type as that of the productionapparatus 100 of FIG. 1. In Examples 1, 2, and 4 in which the weight wasthe same, the amount per unit time of the glass fiber F cut by thecutting device 20 (the amount of the glass chopped strands S produced)was the same, and the amount per unit time of the binder A sprayed bythe binder sprayer 40 was the same.

The production conditions and test results of Examples 1 to 4 are shownin the following Table 1.

TABLE 1 Example Example Example Example 1 2 3 4 Weight (g/m²) 107 107 90107 Conveying speed in first 69.0 71.3 71.3 73.5 conveying step (m/min)Conveying speed in 76.6 76.6 76.6 76.6 second conveying step (m/min)Speed difference (m/min) 7.6 5.3 5.3 3.1 Tensile strength in 153 136 109154 width direction (N) Tensile strength in 206 175 149 171 longitudinaldirection (N) Tensile strength ratio 0.74 0.78 0.73 0.90 (widthdirection/ longitudinal direction)

In all of the examples, the weights were within the range of 50 to 150g/m². The conveying speed of the first conveyor in the first conveyingstep was set to 69.0 m/min in Example 1, 71.3 m/min in Example 2, 71.3m/min in Example 3, and 73.5 m/min in Example 4. The conveying speed ofthe second conveyor in the second conveying step was set to the samevalue, 76.6 m/min, in Examples 1 to 4. In all of the examples, theconveying speed in the second conveying step was higher than theconveying speed in the first conveying step, and the difference betweenthese speeds (hereinafter referred to as a “speed difference”) was 7.6m/min in Example 1, 5.3 m/min in Example 2, 5.3 m/min in Example 3, and3.1 m/min in Example 4, i.e., was within the range of 3 to 8 m/min inall of the examples. The tensile strength was measured by conducting atensile rupture test according to the Japanese Industrial Standards(Section 7.25 of JIS R3420 (2006)), where the width of a test specimenwas 150 mm. The average value of test results where n=40 was calculated.

The following findings were obtained from the examples.

(1) The ratio of the tensile strength in the width direction to thetensile strength in the longitudinal direction (the width direction/thelongitudinal direction) of the example glass chopped strand mat was 0.74in Example 1, 0.78 in Example 2, 0.73 in Example 3, and 0.90 in Example4. In all of the examples, the tensile strength ratios were within therange of 0.73 to 1.00.

(2) The glass chopped strand mats of the examples had such a sufficienttensile strength that a break or a molding defect does not occur duringthe molding process.

(3) When the weights were the same, the tensile strength in thelongitudinal direction increased with an increase in the speeddifference.

(4) When the weights were the same, the ratio of the tensile strength inthe width direction to the tensile strength in the longitudinaldirection (the width direction/the longitudinal direction) decreasedwith an increase in the speed difference.

(5) When the weights were the same, a definite influence due to thespeed difference on the tensile strength in the width direction was notverified.

(6) When the weights were different, the tensile strengths in the widthand longitudinal directions and the tensile strength ratio (the widthdirection/the longitudinal direction) increased with an increase in theweight irrespective of the magnitude of the speed difference.

As a comparative example, a glass chopped strand mat was produced underconditions that the speed difference was 12.0 m/min, which exceeds theupper limit value of the present invention, so that the ratio of thetensile strength in the width direction to the tensile strength in thelongitudinal direction (the width direction/the longitudinal direction)became less than 0.74. As a result, the weight was much lower than theset value, and a number of voids occurred. Therefore, the yield of theproduct decreased, leading to an increase in producing cost.Alternatively, a glass chopped strand mat was produced under conditionsthat the speed difference was 0.0 m/min, which is lower than the lowerlimit value of the present invention (i.e., the conveying speed of thefirst conveyor in the first conveying step and the conveying speed ofthe second conveyor in the second conveying step are set to be equal toeach other), so that the ratio of the tensile strength in the widthdirection to the tensile strength in the longitudinal direction (thewidth direction/the longitudinal direction) became equal to 1.00. As aresult, a number of noticeable wrinkles occurred in the mat surface, andthe tensile strength was not sufficient. Therefore, the product had abad balance between tensile strength and flexibility.

Next, the glass chopped strand mats of Examples 1 to 4 were put on bothsides of a foamed urethane sheet to produce automotive molded ceilingmaterials. When the glass chopped strand mats of the examples weretemporarily unwound in the producing process of the automotive moldedceiling material, these glass chopped strand mats were smoothly unwoundwithout being broken in the width direction due to tension. Also, in themolding process of the automotive molded ceiling material, a moldingdefect such as a sink mark did not occur in the surface of theautomotive molded ceiling material.

As described above, it has been found that the glass chopped strand matof the present invention has a good balance between flexibility andtensile strength, i.e., has both a good flexibility and a good tensilestrength. It has also been found that by using the glass chopped strandmat of the present invention, recent automotive molded ceiling materialswhich have excellent design and reduced weights can be produced. When anautomotive molded ceiling material is produced using the glass choppedstrand mat of the present invention, the yield and production efficiencyare good, leading to a reduction in producing cost.

INDUSTRIAL APPLICABILITY

The glass chopped strand mat of the present invention and a glasschopped strand mat obtained by the glass chopped strand mat productionmethod of the present invention is applicable to automotive moldedceiling materials, and in addition, interior materials for othervehicles and interior materials for buildings.

REFERENCE SIGNS LIST

-   -   10 CHAMBER    -   20 CUTTING DEVICE    -   30 DISTRIBUTION CONVEYOR    -   40 BINDER SPRAYER    -   50 FIRST CONVEYOR    -   60 SECOND CONVEYOR    -   70 HEATING FURNACE    -   80 COLD PRESS ROLLER    -   90 WINDING MACHINE    -   91 FRONT SKIN    -   92 FOAMED URETHANE SHEET    -   93 BACK SKIN    -   100 GLASS CHOPPED STRAND MAT PRODUCTION APPARATUS    -   200 AUTOMOTIVE MOLDED CEILING MATERIAL    -   F GLASS FIBER    -   S, S′ GLASS CHOPPED STRAND    -   A BINDER (RESIN POWDER)    -   M GLASS CHOPPED STRAND MAT

The invention claimed is:
 1. A glass chopped strand mat produced byforming glass chopped strands into a sheet, wherein the ratio of atensile strength in a width direction to a tensile strength in alongitudinal direction (the width direction/the longitudinal direction)of the glass chopped strand mat is at least 0.73 and less than 1.00,wherein the tensile strength in the width direction is 80 N to 154 N asmeasured in a tensile rupture test conducted according to the JapaneseIndustrial Standards (Section 7.25 of JIS R3420 (2006)), where width ofa test specimen is 150 mm.
 2. The glass chopped strand mat of claim 1,wherein the glass chopped strands have a weight of 50 to 150 g/m², wherethe weight is the mass per unit area.
 3. A method for producing anautomotive molded ceiling material, comprising: a layering step ofputting the glass chopped strand mat of claim 1 on one or both sides ofa flexible base sheet.
 4. A method for producing an automotive moldedceiling material, comprising: a layering step of putting the glasschopped strand mat of claim 2 on one or both sides of a flexible basesheet.
 5. An automotive molded ceiling material including a glasschopped strand mat produced by forming glass chopped strands into asheet, and a flexible base sheet on one or both sides of which the glasschopped strand mat is provided, wherein the ratio of a tensile strengthin a width direction to a tensile strength in a longitudinal direction(the width direction/the longitudinal direction) of the glass choppedstrand mat is at least 0.73 and less than 1.00, wherein the tensilestrength in the width direction is 80 N to 154 N as measured in atensile rupture test conducted according to the Japanese IndustrialStandards (Section 7.25 of JIS R3420 (2006)), where width of a testspecimen is 150 mm.